let cr :string ="\r\n===========================\r\n"
let greeting : string = "Hello World.";

/* 如下用法，将在编译时报错
greeting = 123 
*/ 
console.log(cr,greeting);

let testScore : number = 100;
/* 如下用法，将在编译时报错
testScore = "hello" 
*/ 

if( testScore >= 60){
  console.log(cr,"考试通过");
}
console.log(Number.MAX_VALUE,Number.MIN_VALUE);
console.log(Number.MAX_SAFE_INTEGER,Number.MIN_SAFE_INTEGER);

// 标识符可以使用a-zA-Z$_开头，不能用0-9开头

let typeArr  =["any","unknown","never","boolean","number","bigint","string","array",
  "tuple","function","object","class","泛型、类型别名、联合类型、交叉类型"
];

console.log(cr,"typescript的类型有这些：")
typeArr.forEach(element => {
  console.log(element)
});